There are lots of them, of various kinds. Many specialize in certain genres or types of writing such as the SCBWI (Society of Children's Book Writers and Illustrators) conferences and those for people who write - or want to write - for the Christian market. There are lots of other categories, too. Some conferences are relatively inexpensive and may only last a few hours or a weekend while others cost more and last for days. Some have editors and agents available to consider your work, which may or may not cost an additional fee, and others just help you learn more about the craft and business of writing.
If you're a beginner, I suggest you start with a small, inexpensive conference and learn all you can there before moving up to the bigger ones. If you've been published frequently you may even get to be a conference speaker. I've led workshops at quite a few small conferences. That's a good way to become better known.
If you are planning to attend a writers conference of any sort for the first time I suggest you go to the website of my friend, John Vonhof at www.WritersConferenceGuidelines.com for some helpful information.